How do I register for Self Assessment?
Register online with HMRC by 5 October 2026 if you need to send a return for the 2025/26 tax year and have either never sent one before, or registered earlier but did not need to send one for 2024/25. If you tell HMRC after that date, you could get a penalty.
Figures checked against gov.uk on . General information, not tax advice.
At a glance
- Registration deadline for the 2025/26 return
- 5 October 2026
- Sole trader trading income that triggers a return
- More than £1,000 before expenses
- Other income (trading or property), gross
- Over £2,500: register for Self Assessment
Who needs to register
You register when you are new to Self Assessment: you are self-employed above the £1,000 line, you rent out property, or you have another reason to send a return. gov.uk lists the reasons on its page about who must send a tax return, and it is worth checking that list before you register, because many people with a small side income do not need to.
If you registered in the past but did not need to send a return for 2024/25, gov.uk says you may need to reactivate your account rather than register from scratch.
Reasons to register even if you are not required to
gov.uk says you can choose to send a return to prove you are self-employed, for example for Tax-Free Childcare or Maternity Allowance, to pay voluntary National Insurance contributions, or to claim Income Tax relief on maintenance payments.
Registering is separate from filing: the 5 October date is about telling HMRC, while the return itself is due by 31 January 2027 if you file online.
What you get after registering
HMRC issues a Unique Taxpayer Reference. gov.uk says you usually get it by post around 15 days after you register, and longer if you live overseas, so do not leave registration to the last week.